One of the major expenses for wireless communications network service providers is the backhaul of traffic, which is rapidly increasing due to the introduction of high speed data services. There is therefore a need to add transmission capacity to the backhaul of wireless communications networks in order to handle the increasing data traffic and other traffic such as voice traffic. One solution which has been considered is to use both microwave backhaul and fibre optic backhaul in the lower radio access network of a wireless communications network, in place of the conventional microwave backhaul. However, while a fibre optic backhaul provides a much higher traffic transmission capacity than a microwave backhaul, the costs of implementing a fibre optic backhaul are considerably higher than a microwave backhaul. A further solution, which offers the higher transmission capacity of a fibre optic backhaul but without the same installation costs, is a free space optics backhaul. A free space optics transmission system works in a similar way to a fibre optic transmission system, with the only difference being that the optical signals are propagated in air as the transport medium. Whilst free space optics backhaul systems offer higher transmission capacity, they can be less reliable than microwave backhaul due to their greater susceptibility to failure due to adverse weather conditions. A solution to this has been proposed in US 2004/0208591 in which a hybrid wireless optical and radio frequency communications link is provided. The optical (freespace optics) link is used to provide the primary transmission path for traffic, whilst the radio frequency link provides a backup path for traffic and a primary path for control and status signaling. When atmospheric conditions degrade the optical link to the point where optical signal transmission fails, transmission is switched to the radio frequency link.